SMELL. By: Col & Lincoln

Transcription

1 SMELL By: Col & Lincoln

2 Anatomy Of Sense The Sense of smell relies heavily on Chemoreceptors used to detect Odorants The organ of smell itself is the olfactory epithelium The Epithelium covers the nasal concha contains millions of Olfactory receptor cells Olfactory receptor cells send impulses (once detected) along their axons to the olfactory bulb of the brain At the base of the epithelium are the basal cells Each olfactory receptor cell is a bipolar neuron, each covered in a thin layer of mucus, which is designed to capture and dissolve odorants The both slender and unmyelinated axons of the olfactory receptor cells gather into small fascicles The filaments of the olfactory nerves synapse with mitral cells located in complex structures called glomeruli The Frontal lobe is responsible for recognizing odor

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4 Physiology Of Sense Smell (or Olfaction) is used by many animals for different purposes In order to smell an odorant, it must be volatile, or in a gaseous state. It becomes so by dissolving first in the humidity of the yellow pituitary. When an odorant diffuses to the sensitive ends of olfactory neurons in the mucous membrane, a process called transduction occurs once the odorant attaches to chemoreceptors on the cilia. This triggers a signal leading to the production of cyclic AMP Flow of these ions causes depolarization of the membrane, generating AP s Each glomerulus represents a certain type of odor signal, while the different odors would activate different subsets of the glomeruli Receptors and brain pathways for taste and smell are independent but do interact Interestingly enough, smell is linked closest to memory due to the connection of the olfactory bulb to the limbic system.

5 Step 1: Vaporization and Dissolution Odor molecules in vapor reach the nostrils through Inhalation. They quickly dissolve in the mucus on the roof of each nostril. Mucus is created by mucus membranes which contain mucous glands

6 Step 2: Detection Within the olfactory epithelium lies the olfactory receptor neurons, with cilia protruding from the epithelium. Attached to these cilia are chemoreceptors able to detect thousands of different odors.

7 Step 3: Transduction Olfactory receptor neurons send the information, once received by the odorants and chemoreceptors, down their axon and through the cribriform plate of bone. These Signals reach the back of the nose, where the olfactory bulb, at the Frontal Lobe, is located.

8 Step 4: Sending Signals From the Olfactory Bulb, signals are sent directly to limbic system structures (Parts of the brain that are responsible for emotions and memories), as well as higher functioning centers that modify conscious thought (Neo-Cortex)

9 Step 5: Association Both the Neo-Cortex and Limbic System Structures perceive odors and associate them to people, places, and events you have experienced before.

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11 Homeostatic Imbalances Hyposmia - a reduced ability to detect odors Anosmia - the inability to detect odors at all Phantosmia - an olfactory hallucination, involves smelling an odor that isnt actually there. Parosmia - Inability of the brain to properly identify an odors natural smell Dysosmia - The two above being able to be classified as such, Dysosmia is classified as any disorder relating to the distortion of the sense of smell.

12 Imbalances P.2 Hyposmia and other nasal problems are mainly caused by allergies, nasal polyps, viral infections,and head trauma. Lifelong hyposmia/anosmia may be caused by Kallmann Syndrome, a rare genetic disorder in which puberty is delayed and the sense of smell is damaged. Phantom smells may come after a head injury or upper respiratory infection

13 Important Vocabulary Within Presentation - Olfaction (the science term for smell) - Odorant (the scent or scents that the olfactory system processes) - Mitral Cell (a unipolar cell that processes information in the brain) - Olfactory Cell (a bipolar, sensory cell that transfers information to the brain) - Olfactory Epithelium (Pseudostratified epithelium that contains olfactory receptor cells, supporting cells, and mucus-secreting glands) - Cribriform Plate (a plate that falsely creates a sagittal cut in the skull located in the frontal bone) - Ethmoid Bone (at the root of the nose forming from the cranium) - Superior Nasal Cavity (the structure for the intake of olfaction) - Cilia (short, microscopic, hairlike structure inside the nose) - Mucus (a slime-like substance made by mucus membranes for multiple uses)

14 ACTIVITY TIME!

15 Sources The Senses of Taste and Smell Rely on Similar Sets of Sensory Receptors. Campbell Biology, by Jane B. Reece and Neil A. Campbell, Pearson Education, Inc., P Human Anat. and Phys. P eaca612da0fc4f